This invention relates to connectors for making electrical connections to electrical components, and, more particular, to a flexible interconnect circuit having electrical traces supported on an electrically insulating substrate.
One of the continuing trends in the electronics and electromechanical apparatus industries has been reducing the size of many components and types of apparatus. There are many reasons to strive for reduced size, but generally miniaturization increases the speed of operation of electronic devices, reduces the cost of components and apparatus, and increases the numbers of functions that they can perform.
As the size of the components is reduced, the difficulty in providing electrical interconnections between components and to components becomes greater. Assuming that the number of required external connections for any particular component remains approximately constant even as the size is reduced, the space around the periphery of the device that is available to make the connections becomes smaller. Thus, for example, a 10 fold reduction in component size also reduces the available length of periphery by 10 fold.
Since the linear length and space required to make external connections typically does not scale downwardly, the reductions in component size have prompted many approaches to improved connectability. In one, a flexible connector material called a TAB (for Tape Automated Bonding) flexible interconnect circuit material has been introduced. A TAB circuit electrical connector material includes a flexible insulating support layer, typically made of a plastic material, and particularly a polyimide such as Kapton. Traces of electrically conducting material are formed on the surface of the support layer. The traces are normally made of copper which is electroplated with gold to reduce oxidation.
The TAB circuit bonding approach is widely used to make various types of devices. For example, U.S. Pat. Nos. 3,689,991 and 4,649,415, which are incorporated by reference, describe the use of flexible circuit bonding to semiconductor components. U.S. Pat. No. 4,635,073, which is incorporated by reference, describes the use of flexible circuit bonding for thermal ink jet printer print heads. This approach of flexible TAB circuit bonding is particularly suited for manufacturing large numbers of identically configured circuits because the bonding material is manufactured in long strips or rolls and the bonding operation is automated.
In use, the custom flexible interconnect circuit is fabricated, and then it is attached to the component for which it is designed. The component typically is placed within the periphery of the interconnect circuit, either within an aperture cut through the interconnect circuit or mounted directly upon the plastic support of the interconnect circuit. One end of each trace of the interconnect circuit is bonded to the appropriate bonding point of the leads of the component, and the other end provides external access.
Although its use has greatly increased the efficiency of many manufacturing operations, the flexible circuit bonding approach has drawbacks in practice. It is difficult to place more than one component within the periphery of a flexible circuit, due to manufacturing problems that are encountered in forming the traces that run between the components on the flexible circuit. Accordingly, there is a need for an improved manufacturing approach to producing flexible interconnect circuit material, which permits the placing of more than one component on the circuit. The present invention fulfills this need, and further provides related advantages.